This invention relates in general to an improved planar, and preferably disc shaped snap-acting spring capable of overcenter snap-action to provide precise reciprocating motion for linear positioning devices, pistons, valves or fasteners or to provide radial spring support and suspension for rotating machinery or vibration absorbing devices, and still more particularly, to a snap-acting spring element capable of being adjusted to change its snap-acting characteristics, and furthermore, capable of being mechanically biased to provide monostable operation.